Method of phosphor surface coating



United StateS Patent 3,sZZ,071 METHoD of PHoSPHoR SUREACE CoATING YoShiynki Yokofa and TakaShi Miy2gaW2, fnfafsnka-Shf, !faSufo Tanaka, Tokyo, and Tafuki Tofii, f)daWafa-Shi, Japan, assignofS fo ])af l`Tippon Tofyo I(2bushiki I(3iSh2, I(onohanaku, ()sakaShi, Japan Eiled Aug. 19, 1966, Sef. No. 573,63s Inf. CL H0li Z/20 U.Sl CL 11733.s Z Claims ABSTRACT of THE DISCLoSURE The photoSenSitive pfopeftieS and Stability of phoSphof sluffieS USed in photopfinting afe in1pfoved by Sufface coating a phosphof adapted fof being appHed to the innef sufface of a cathode fay tube vvith Slightly Soluble acidic oXides, Said acidic oXides being oXideS of at leaSt one eleInent Selecfed ffofn the gfoup conSisfing of bofon, alun1inun1, titaniUn1, vanadiun1, gallilln1, gefInaniuIn, afSenic, niobium, Inolybdenum, tin, antiInony, tantaluIn and tungSten.

ThiS invention felateS to iInpfovefnents in the photo Sensitive fopefties of phosphof SuSpenSionS (hefeinaftef fefeffed fo aS phoSphof sluffieS) in which the phoSphof iS diSpefSed in a polyviny1 alCohol solution fendefed hotoSenSitive by a phofoSenSitiZef, e.g. an1n1oniUn1 bichfoInate, fof USe in photopfinting, and in phosphof Scfeens Using the Said phosphof SluffieS.

Phosphofs which afe known to be USed in the fofmation of phoSphof scfeenS fof photopfinting include, fof eXample, the phoSphofS fof uSe in the phosphof Scfeen of a colof televiSion picfufe fobe SI1ch aS blue efnitting Silvof acfivated Zinc S111fide phoSphof (ZnS=Ag), gfeen enliftiflg Silvef activated Zinc-cadium Sulfide phoSphof ((Zn (:d)S=Ag) and fed enitting Silvef activated Zinc cadminn1 Sulfide phoSphof ((Zn,Cd)S:Ag), eUfopiUn1 activated yttfillII1 vanadate phoSphof (Yvo =Eu), eufopiufn activated ytffi11ff1 oxide phosphof (Y :E11), and eufopinm activated gadolinium oXide phoSphof (Gd 0 :Eu).

TheSe phoSphofS afe applied aS phosphof SluffieS in the foffflation of phosphof Scfeens. vvhen llSed aS phosphof SlI1ffieS vvith of vvithoI1t sufface tfeatfnent With phosphate of Silicate, the phoSphofS invite cheff1ical feaction of physical of chefflical absofption With the ammoniom bi chfofnate con1ponent in the phoSphof S111ffy, and Sofne phosphofs cause conSidefable changeS in the viScoSity of the s111ffy vVith tiffle. Fof this feason, it haS been dinco1t to fofm unifofn1 and hoInogeneous phoSphof ScfeenS ffom the conventional S111ffieS becauSe of the changes in the s111ffy viScosity and, in addition, fepeated USe of SI1ch phosphof SluffieS haS nof been possible, If phosphof Scfeens afe IIlade, the photoSenSitivity fof fiXing the ScfeenS iS decfeaSed becauSe of the afofeSaid effectS of the phosphofS Upon the bichfofnate ions Sefving aS the photoSenSitive agent in the phoSphof slI1ffies.

To nlake up fof the decfeaSe of the photosenSitivity, it haS been pfoposed to add an1n1oniuII1 bichfoInate in an anUnt IT1ofe than essentially fequifed to the phosphof Sluffy Hovvevef, bichfon1ate ions added in Such a lafge aInount have an advefse effect on the en1iSSion bfight neSS of the phoSphofs, and conSequently, phosphof sCfeenS fflade ffom the conventional phoSphof SluffieS have low en1isSion bfightness.

ESpeciany When phoSphof ScfeenS afe to be fofIned of fafe eafth oXide phoSphofS SUch aS Y 0 :Eu phosphof Gd 0 :Eu phosphof, etc,, the phosphofS exhibit poof stability if1 the phosphof Sluffies. In Shoft the phosphof s1UffieS I1SiI1g the aboveInentioned phoSphofs afe chafac tefized by conSidefable changeS of viScosity, photoSenSi tivity, and othef pfopefties vvith tifne due to the detefiofation of the ph0Sphof sufface It is an object of the pfeSent invention to ifflpfove the Stability of the phoSphof sluffieS by the action of a ceftain feagent which is added eithef vvhile the phoSphofS afe being SUbiected to a ceftain Sufface tfeatn1ent of dUfing the pfepafation of the SluffieS,

Anothef object of the invention iS to ifnpfove the photo senSitivity of phosphof ScfeenS by incfeasing the SenSifivity of the phoSphof sluffieS.

A fnfthef objecf of the invention is to pfovide phoS- phofS capable of foffning phosphof ScfeenS vvhich attain gfeafef eIT1ission bfightneSS Undef eXcitation by an elec tfon beam than that of Scfeens uSing conventional phoS phofs.

sufface tfeatn1ents of coating pfoceSSeS vvhich have hefetofofe been employed fof phosphofS include coating with silicate of phosphate fof inlpfoving the diSpefSion of phosphofS in Solution, adhesion on a glaSS face, and pfotection of the phoSphofS againSf inpufities. Howevef, phosphof Sluffies fofII1ed ffofn phoSphofs tfeated aS above have Shown n0 changeS in the fopefties ffon1 the Un tfeated ones.

The coating pfoceSS accofding to fhe PfeSent invention cofnpfiSeS fofnling of depoSiting a Slighfly Soluble acidic oXide of a salt thefeof on the phosphof SUfface. when phoSphof Sluffies afe pfopafed ffoIn the phosphofS ffeated aS above, the SlI1ffies afe vven pfotected against viScosity changeS and can be used Sevefal tiffleS fepeatedly ovef an extended pefiod of tinle. Mofeovef, the phoSphof ScfeenS foffned of the coated phoSphofs can have incfeaSed phofo senSitivity fof xing and, if the expoSufe conditionS afe kept Unchanged, the phoSphof SlI1ffies can contain Sfnanef amountS of aff1IT1oniun1 bichfofnate than thoSe in the slI1ffieS of phoSphofS pfepafed by Conventional pfoceSS. Th11S, the aInount of fesidua1 ChfofI1ium in the peffected phoSphof ScfeenS iS SIIlallef and the feduction of bfight neSS of phosphofS due to the pfesence of chfoIniUIn is leSS than those in the conventional ScfeenS, and fhefefofe bfightef ScfeenS afe obtained in accofdance vvith the in vention. vVhen the san1e afnoUnt of an1fnoniun1 bichfonlate aS in ofdinafy sluffy is added, the phosphof Sluffy pfePafed by the uSe of a phoSphof tfeafed accofding to the invention pefn1itS a SUbStantial Shoftening of the eX poSufe tifne and hence of the opefating tifne.

TheSe and ofhef advantages and featIlfeS of this in Venfion vViH be bettef undefSfood aS the descfiptfon pfo ceeds with fefefence to the accom anying dfawingS in which:

FIG. 1 iS a diagfafn Showing the pH aS a function of tine of ph0Sphof SlI1ffieS pfepafed ff()IT1 an eufopium activated ytffinIn oxfde phosphof coated with 5 by vVeight of tungsten ffioXide (Wo (cufve zz) and ffom the Sanle phoSphof but which vas not coated (cufve Z));

FI(r- Z iS a diagfan1 showing changes of eInission bfightneSS (cufve zz) With fifing feInpefatufe of an eufo piun1 activated ytffiun1 oXide phoSphof in the coufSe of Coating vvith by vveight of tungsten tfioxide (vV0 and the pH aS a function of tiIne (cufve f) of a phosphof Sluffy pfepafed ffom the phoSphof; and

FIG. 3 iS a diagfaIn explaining the felafionShip between fhe fiIne of eXpoSufe fo nlffaviolet light iffadiated fo cauSe adheSion to the face plafe of a cathode fay tube, of phosphof scfeenS fofIned of silvef activated zinccadfniUm Sulfide phosphof coated vvith 2% by Weight of gefmaniUm oXide (Geo (cufve o) and of the SaIne phoSphof nof coated (cufve Z)), and the dof size of the phoSphofS obtained aftef developmenf.

In genefal, accofding to the pfeSent invention, fhefe afe two fnothodS of foffning of depositing a SHghtly sol]Jble acidic oXide of itS Salt on the phosphof Sufface. 

